This application is based upon and claims the benefit of Japanese Patent Application No. 2000-125843 filed on Apr. 26, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
This invention relates to an infrared image sensor.
2. Description of the Related Art
Thermal type infrared sensors are usable in a non-cooled state for general-purpose, and have various types such as a thermopile type and a bolometer type. For example, JP-A-8-43208 proposes a bolometer type infrared sensor capable of measuring a temperature by utilizing a change in resistance.
In this kind of bolometer type infrared sensor, it has been studied to realize an infrared image sensor capable of providing a stable thermal image by comparing an output of an infrared detecting element and an output of a temperature compensation element (reference element). The temperature compensation element has the same characteristics as that of the detecting element and disposed at a position where it does not receive infrared radiation.
However, it is difficult to provide stable output due to a practical difference in characteristics between the infrared detecting element and the temperature compensation element. In general, a measuring instrument such as a Peltier element is used to keep an environmental temperature constant and to make the output stable. However, this method requires high cost, and large electric power consumption. Further, it is difficult to keep the environmental temperature constant even by the Peltier element in a space such as a passenger compartment of a vehicle where the environmental temperature varies largely.
The present invention has been made in view of the above problems. An object of the present invention is to provide an infrared image sensor capable of providing stable output even when an environmental temperature varies.
According to the present invention, an infrared image sensor has a plurality of sensor elements provided on a semiconductor substrate for providing thermal image data by receiving infrared radiation from a measurement member to measure a temperature of the measurement member, and a plurality of temperature compensation elements provided on the semiconductor substrate.
Each of the plurality of temperature compensation elements is arranged to be adjacent to or to overlap with a corresponding one of the plurality of sensor elements, for performing temperature correction to an output of the corresponding one of the plurality of sensor elements.
Accordingly, even when a temperature of the substrate varies, the difference in temperature between the each temperature compensation element and the corresponding one of the sensor elements can be minimized, thereby providing stable output.